A comprehensive study is proposed to aid in understanding the fate and transport processes that affect the migration of contaminants in the environment. The other goal is the development of innovative risk-based methodologies and computational tools, which can be used to simulate the migration patterns of contaminants in the environment. For this purpose, we propose the development of modular computational tools, which will include mechanistic models for surface water, groundwater, air and other engineered conduit pathways. The proposed modular models will be linked to risk-based exposure analysis models using probability and possibility theory. The mechanistic modeling will be used to understand and link the effect of environmental factors on spatial and temporal spread of contaminants in the environment. The risk-based exposure analysis will be used to quantify the health risk through standard exposure pathways, and will be based on variability and uncertainty in input parameters as well as uncertainty in conceptual models developed. The goal is to provide managers and health scientists, risk-based modular simulation tools to evaluate contaminant concentration levels in the environment at the human contact level so that preventative measures and decisions can be tied to transparent and reproducible data.